Program Information
Voxel-Based Dosimetry and Validation of Yttrium-90 Microsphere Therapy Using Emission Tomography Imaging
P Potrebko1*, R Shridhar1 , M Biagioli1 , M Cross2 , T Lazarakis2 , G Andl2 , T Fox2 , (1) Florida Hospital Cancer Institute, Orlando, FL, (2) Varian Medical Systems, Atlanta, GA
Presentations
TU-FG-205-11 (Tuesday, August 1, 2017) 1:45 PM - 3:45 PM Room: 205
Purpose: To validate and demonstrate the efficacy of voxel-based ⁹⁰Y microsphere dosimetry using the local deposition method (LDM) combined with SPECT/CT imaging.
Methods: A commercial software imaging and dosimetry platform (Velocity, Varian Medical Systems) was evaluated on six target volumes for five microsphere patients that were imaged using optimized bremsstrahlung SPECT/CT acquisition and reconstruction protocols. For each case, the ⁹⁰Y SPECT/CT was registered to a diagnostic MR or CT using deformable or rigid registration algorithms. The ⁹⁰Y voxel-based dose distribution was computed using the LDM with known injected activity and corrected for the lung shunt fraction. Calculated point doses from thirty randomly selected voxels within the dose cloud were compared to a secondary LDM calculation performed by research code interfaced with the CERR software platform.
Results: The prescription doses, injected activities, and tumor volumes ranged from 145-280 Gy, 1.330-2.671 GBq, and 8.5-73.8 cc, respectively. The commercial platform allowed the visualization of the ⁹⁰Y isodose distributions on any of the registered image datasets and the calculation of dose-volume histograms for the contoured structures. The dose module was able to demonstrate the extremely high local doses that are characteristic of blood-flow directed brachytherapy. The mean and maximum GTV doses ranged from 204-606 Gy and 343-1387 Gy,respectively. The mean tumor V190Gy was calculated to be 77.0%, a known predictor of favorable response. The mean dose difference between the commercial and research calculation was 0.2% across all sampled voxels.
Conclusion: The implementation of the LDM dose algorithm for quantitative voxel-based ⁹⁰Y patient dosimetry displayed acceptable accuracy. The ability to perform deformable/rigid image registration and calculate ⁹⁰Y isodose distributions and dose-volume histograms points to the clinical utility of patient-specific absorbed dose calculations for radionuclide therapy. With further development, this method could potentially be used to facilitate multi-modality therapy in combination with external beam radiation.
Funding Support, Disclosures, and Conflict of Interest: P. Potrebko, M. Biagioli, and R. Shridhar have a consulting agreement with Varian Medical Systems
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